Remove the Tenderflake frozen pie shell from the freezer and let it come to room temperature, about ten to fifteen minutes.
Using a fork, poke holes all over the pie shell.
Bake at 400 degrees for 10-12 minutes, until golden brown. Remove from oven and let cool completely.
In a medium bowl, lightly whisk the egg yolks to combine; set aside.
In a medium saucepan, whisk together the whole milk, sugar, cornstarch, salt and matcha powder. Bring to a simmer (do not boil) and cook, whisking constantly, about 5 minutes.
Whisk a quarter of the hot green tea milk mixture into the egg yolks to combine; then slowly whisk in the remaining milk mixture.
Return mixture to the saucepan and cook over medium-high heat, whisking constantly, until custard thickens and bubbles appear in the center, 3-5 minutes.
Transfer to a medium bowl and cover with plastic wrap, pressing it directly onto the surface to prevent a “milk skin” from forming!
Chill in the freezer until completely chilled – about 40-45 minutes. (You can make the filling a day in advance, stored in the refrigerator.)
Pour the green tea pie filling into the cooled pie shell, using an offset spatula to spread it evenly.
Set the pie in the fridge until ready to pipe with whipped cream.